Energy harvester

Abstract

An energy harvester is provided. The energy harvester includes a current-voltage converter, a voltage-PWM converter, an analog multiplier, a sample-hold circuit, an α-generator, and a fractional open-circuit voltage circuit.

What is claimed is: 
     
       1. An energy harvester comprising:
 a current-voltage converter configured to sense a current of a solar cell in a current mirror method while charging an output of the solar cell in a capacitor, and to calculate an output voltage (V) using the sensed current; 
 a voltage-PWM converter configured to generate a pulse width modulation (PWM) single pulse by comparing the output voltage calculated by the current-voltage converter with a ramp voltage; 
 an analog multiplier configured to determine an output power (P) of the solar cell by multiplying an output voltage of the solar cell by the PWM single pulse; 
 a sample-hold circuit configured to measure a maximum output power in real time by comparing the output power (P) from the analog multiplier with a maximum power value, and to measure a voltage (V MPP ) of the solar cell generating the maximum output power in real time; 
 an α-generator configured to generate a digital bit having n-bit using an open circuit voltage of the solar cell and the V MPP  obtained from the sample-hold circuit; and 
 a fractional open-circuit voltage (FOCV) circuit configured to include a plurality of capacitors and to charge and redistribute charge to the capacitors using the digital bit of the a-generator and the open circuit voltage of solar cell. 
 
     
     
       2. The energy harvester of  claim 1 , wherein in the current-voltage converter,
 the output voltage (V) is obtained by multiplying the current sensed by the solar cell by a resistance. 
 
     
     
       3. The energy harvester of  claim 1 , wherein in the voltage-PWM converter, when the sensed current is greater, a width of the PWM single pulse becomes wider, and when the sensed current is smaller, the width of the PWM single pulse becomes narrower. 
     
     
       4. The energy harvester of  claim 1 , wherein the sample-hold circuit includes the plurality of capacitors, and
 wherein when the output power is greater than the maximum power value, the output power is stored in one of the capacitors. 
 
     
     
       5. The energy harvester of  claim 1 , wherein the a-generator generates  8 -bit, and
 wherein α<7:0> that satisfies the a value obtained by dividing the V MPP  by the open circuit voltage is generated.